A wireless control system includes a base station which performs wireless communication with a mobile terminal. The base station includes a wireless unit which performs wireless communication with a mobile terminal, and a baseband signal processor which performs baseband processes, such as modulation and demodulation of signals. The mobile terminal is called user equipment (UE).
In order to perform easy maintenance of the base station and reduce maintenance cost, a wireless unit and the baseband signal processor are sometimes installed separately from the base station. The wireless unit separated from the base station is called a remote radio head (RRH). The wireless unit is a kind of transceiver. The baseband signal processor separated from the base station is called a baseband unit (BBU).
In order to interconnect the RRH and the BBU which were provided by different vendors, the protocol interface in the communication between the RRH and the BBU has been standardized. An example of the standardized interface is the common public radio interface (CPRI).
Multiple UEs perform wireless communication with a single RRH. Multiple RRHs perform packet communication with a single BBU. The plurality of BBUs are coupled to a single management server which manages a network of the entire wireless control system. The management server functions as an element management system (EMS) which monitors the entire amount of data traffic, and it functions as a self organizing network (SON) which automates installation and operation of the base station. The SON optimizes the operation of the BBU and the RRH in accordance with the information about the amount of data traffic acquired by the EMS. Techniques about the wireless communication system are disclosed in the following literatures.
Japanese Laid-open Patent Publication No. 2007-274048 and Japanese Laid-open Patent Publication No. 2010-509816 are examples of related art.
In the wireless communication system, each UE has the status of use which is different from those of other UEs. The status of use of each UE changes over time. Therefore, the operation rate of the RRH which performs wireless communication with plurality of UEs and the operation rate of the BBU which performs packet telecommunication with multiple RRHs also change over time. However, since the BBU which performs packet telecommunication with a single RRH is fixed, the packet processing of the RRH coupled to the BBU cannot be distributed to other BBUs no matter how the operation rate of that BBU is low.